Signal Identification Guide

This wiki is intended to help identify radio signals through example sounds and waterfall images. Most signals are received and recorded using a software defined radio such as the RTL-SDR, HackRF, BladeRF, Funcube Dongle, USRP or others.

Anyone can edit this wiki, so if you see missing or wrong information please feel free to correct it by clicking the 'edit with form' button at the stop of the signals page. When doing an edit you will be asked to answer a very simple spam prevention question which will appear at the top of the screen after clicking on Save page.

You can also discuss the signals by using the discussion tab at the top of every page, or just by using the comments box at the bottom of this page (note that the comments section will be periodically pruned to reduce its length).

If you would like to contribute an example signal, please consult the Adding An Example Signal page. If for some reason you cannot use the form, please contact me at rtlsdrblog__AT__gmail__DOT__com and send a waterfall image, sound or small IQ sample and any information about the signal that you have. Note that it will probably take me 3 - 6 months to get to your signal.

Software: There is now the Artemis software available which can be used to display the known reference signals in an easy to access offline format.

ARQ-E (also known as ARQ-1000 DUPLEX) is a Synchronous Full-Duplex ARQ system with each station using a different frequency. ARQ-E3 is a varient that uses a different alphabet encoding. Mainly used by French Military Forces.

AUTOSPEC is a synchronous FEC teletype system used by British costal stations to communicate with North Sea oil rigs. Also known as Autospec-bauer, Bauer, and Autospec Mk1. This signal is most likely phased out.

Used by aircraft as an alternative to secondary radar. It broadcasts (i.e. unsolicited, without waiting for interrogation from a radar station) their GPS position (latitude, longitude) and pressure altitude, their callsign, and their track and ground speed, in separate messages carrying 10 bytes of data each.

Distributed power refers to the placing of an extra locomotive at an intermediate point in the middle section of a train. This locomotive unit is remotely controlled from the lead locomotive, and greatly increases both the pulling and stopping power of longer trains.

Golay-Teleprinting Over Radio (G-TOR) is an FSK proprietary standard developed by Kantronics Inc. and is used by radio amateurs, military (Irish Air Corps/Navy, Mexican army) and governmental agencies (ICRC).

The DFM-06 is a standard radiosonde for most applications. It is perfectly suited for synoptic observations or military applications.
It is designed to measure the profile of atmospheric pressure, temperature, humidity, wind speed and direction, from the surface up to 40 km altitude. Continuous data sets of measurements are sent down to the groundstation by a high quality radio-telemetry link.

IRA-ARQ is a high data rate ARQ FSK system used by Bulgarian, Slovakian, and Czech diplomatic stations. Also known as BULG-ASCII and ASCII-ARQ. The maximum speed of this mode has been seen to reach 1200 bd.

Link-11 (Also known as STANAG 5511, TADIL-A, and MIL-STD-6011) is a Tactical Data Link standard (formerly known as Tactical Digital Information Link (TADIL) used by NATO and the US Military for Maritime Tactical Data Exchange.

CW Morse Code is the simplest form of transmission found virtually all over the RF bands for a variety of uses. The most common use of this is for Call-sign Beacons by both Amateur and Military operators.

PACTOR III introduces 6 speed levels that provide higher throughput and improved robustness compared to PACTOR I and II. PACTOR III is on average 3.5 times faster than PACTOR II. With optimal conditions, PACTOR III becomes over 5 times faster.

I found out what Unknown 453 was, the one that I posted a few weeks ago, it is a police idling signal, apparently the police signal belongs to the remote SDR I was listening to, but I got my own SDR now. So yeah, it is an idling signal for a police walkie-talkie

Project 25 (P25 or APCO-25) is a trunked radio standard developed by The Association of Public Safety Communications Officials International (APCO-25) for use with public safety organizations around the world.

Weatherfax (Also known as Radiofax, HF-FAX, WEFAX, and Weather Facsimile) primarily used worldwide for the dissemination of weather charts, satellite weather images, and forecasts to ships at sea. The oceans are covered by coastal stations in various countries.

Yachta or Yakhta (Russian for 'Boat') T-219 is an analogue voice scrambler. It is unique in that an FSK sync signal is transmitted in the middle of the main signal, with the scrambled voice stream split above and below the FSK signal.

Requested Signals

If you have these signals (or any other not on the list) please either add the waterfall image and sample sound as an MP3 to the wiki and edit the page, or email me at rtlsdrblog__AT__gmail__DOT__com for addition. Please consult the instructions here - Adding An Example Signal.

Unidentified Signals

If you have an unidentified signal that you would like the wiki readers to take a look at please use the form linked below. Include as much information about the signal as you can including frequency, waterfall images, MP3 sound samples, location, bandwidth and anything else you can think of. Please consult the instructions here for more information on adding a signal - Adding An Example Signal.

If you happen to be able to identify a signal, please either edit the wiki (See the Adding An Example Signal page to see how to convert a signal from Unidentified to Identified) or make a note in the wiki discussion page (in the signal page click the discussion tab at the top) or make a comment in the comments area on the Unidentified Signals Database main page.

I'd like to put in a request for info and signal sample on RD-LAP and also on the Motorola MDT signals that preceded the 19.2 kbps rdlap, such as MDC4800.

This is sold by Motorola as part of their DataTAC network package. It used to be active as part of the ARDIS network nationwide, but I believe that has all been retired (maybe still used somewhere? Not 100% sure)

Also, it is still used by some police departments and others with private datatac networks.

I am listening to an unknown signal on 13505 khz AM mode on 10-5-14 at 11:45 am EST which sounds something like a remote control when aimed at a radio(MW or LW). Pulses are short and seem to be "communicating" with each other(close and distant).

Original poster here, no, but I do live in Connecticut. New London County. The 173.226 MHz sounds like a time signal with an incomprehensible identification every 10 seconds, and the 462.407 MHz one sounds like a beacon.

OP here. I don't know why I hadn't thought of this before, but I did a little Googling and found that the two VHF freq's are registered to an address of a town water supply. Street view shows two water tanks/towers at that address, so I'm guessing this is some sort of monitoring system. Saw your video- the waterfall looks similar, at least, to the one I posted, but it didn't sound to me like the same signal.

Unknown ionosonde-like is not an ionosonde, but it is a sounder. Specifically, the 29B6 Over The Horizon Radar sounder is pictured on the University of Twente WebSDR, it makes a paddling noise to check if a frequency is not in use. It isn't very effective since it commonly overlaps HAM bands and SW broadcast bands.

In response to the person who posted about the "Police Idling Walkie Talkie Radio Signal"

I have also found the same signal in the UK which is on the 70cm band it pulses every few seconds with 12MHz BW, I also noticed there is an other pulse signal 30 mhz apart which pulses at a slower pace once every 4 or 5 pulses.

I can extrapolate spectra for a good number of them (esp. the MFSK modulation types) from the audio when I have time. The rest can be placed into new pages or added to sections of pages (POCSAG 512, 1200, etc) for different modes of the same modulation.

General Question:
I'm gauging whether to keep a waterfall-only approach to these articles or if including the spectrum (Like California Smart Meter, DVB-T, and Digital SSTV) above the waterfall as a single image is more preferred.

Waterfalls are easier to get than spectrums, but I have noticed that certain signals sorta need the spectrum as it's a defining characteristic to it's ID (e.g. ATSC and trunked radio signals).

Or, if this is a better idea, having two separate images; one for waterfall and one for spectrum. Thoughts? I don't want to change any more images till I get a clear consensus on this.

Hi Cartoonman,
thanks for your excelent work on this wiki. This will help sigidwiki and Artemis database. A big problem is the frequency and bandwidth forms because actually the concept of range is not entirely implemented. If you are interested to this problem, you are well accepted in the forum of Artemis tool (http://marks...fined-value/).

b. There seems to be quite a bit of confusion on the Cuban HM01 listing. DIGTRX is not a mode - it's an app originally written for digital TV, and folks try to use it to read the data sent by this station (only not very well, from what I hear). The mode is an adaptation of a ham mode known as Redundant Data File Transfer or RDFT. You can find listings for this at the well known Numbers and Oddities website, listed as 'AM/RDFT' as the mode

In the next few days I will be adding a lot of software links. Stay tuned...

Oh lol, thats not a problem. What happens is, the main page actually gets automatically updated every 24 hours. The tag that makes a page appear on the main page is, so as long as that tag exists in the article, by the next server "re-syncing", the article will be placed on the main page.

This only comes into effect when moving the name of the page. for example, moving the page Serdolink to Serdolik. Things like changing the waterfall image, bandwidth, frequency, and description are all done as you do it by direct linking, no need to wait for a server re-sync.

oops, the tag is "Category:Signal". Articles (like ones I just moved a few minutes ago) will have their former entries on the home page removed, and the new entry with the "Category:Signal" tag placed back on the main page with their new name. I just moved Amateur Morse Code Beacon so you can take a look at that for an example.

OK let's say that I used the 'MOVE' tab to rename the Serdolink article to Serdolik. If the entry is then re-indexed, it appears that all the data that was associated with the old entry on the main page is lost (as the beacon article you just moved currently is). That's not a very good scenario.

In addition there are a number of incorrect frequency references on the main page that should be fixed. For example, there is a very specific set of frequencies that HFDL uses that is listed in a PDF file found in the article - the '2.9 Mhz,29 Mhz' listing is misleading since it reads like it could be just those frequencies, and that's simply not true. Another example includes those modes listed as '3 Mhz, 30 Mhz', and again, that's very misleading, since it leads a reader to think that those specific frequencies are used.

Yes that is correct, when the article is moved, all data that was in the old article's location is copied to the new article's location, and the main page's link to the data from the old article is broken. However, this is automatically resolved every 24 hours by the server, as the server resync's articles that have the "Category:Signal" tag, so what happens is, the old article that was truncated of data is removed from the main page, and the new article with the "Category:signal" tag is added to the main page. Sorta like a swap.

The frequency issue is a known thing that me, the admin, and developer of Artemis Aco are aware of. For the time being, the drive is going towards listing frequency range of where the signal exists instead of individual frequencies (since for many of these signals, they can appear at so many different frequencies that it would be pointless to list them all). The format of the site is due to undergo some changes to fit this push, so for the time being, I think that's the direction we're headed with the frequencies. Same goes for bandwidth, for signals that have a range of bandwidths.

What you could do in the case of the HFDL listing is to say something along the lines of 'See Article' in the 'Frequency' column, and let the article itself handle the link for the frequencies. They do change occasionally, and it's usually reported on the HFDL and/or UDXF Yahoo groups

As to the ham stuff - while there is some variation due to different regulations in other countries, amateur radio digital freqs are fairly restricted to certain parts of the bands, at least in the US. Examples of this include the 5 Mhz allocation the US shares with a few countries, but not everyone worldwide has access there. Another one is the 70 Mhz band allocated in the UK, but not in the US.

This website has a basic bandplan, along with the new 5 Mhz allocations that were changed just recently...

You make a very good point; for most cases these frequencies are confined to amateur bands designated by regulations.

I think your idea is great, putting these links under the Frequencies section. You may have to figure out all the little intricacies of different region's band allocations though.

For signals that aren't solely amateur though, especially ones like ALE or OTH that are extremely erratic, or even ionosondes, listing the range that they are found at in the way I mentioned above in my previous comment /\ is, to me, the best way of defining their 'frequency'.

The only little problem that can come up, and this is subject to debate since I'm not an expert in Ham Radio, but individual frequencies of where these signals can be found could potentially change as time goes on, so they will require consistent updating, either by the site owners linked, or by users on this site.

Also, just for the record, http://qrg.globaltuners.com/ <- they have done an outstanding job with categorizing signals found at specific frequencies that are even geolocated. Perhaps we could point users to use their database when looking for specific frequencies of certain signals.

Ham radio frequencies tend not to move a whole lot - yes there are regulatory changes from time to time, but the basic ranges - which that 2nd article would be quite useful for, in the case of HF frequencies - remain pretty much unchanged for quite a while. If the frequency ranges were in the article rather than the main page, it would be a snap to fix.

The problem I see here is one of interpretation - if someone who is new sees something that says '3 Mhz, 30 Mhz', then they might think those 2 specific frequencies are the ones to check, when in fact that's incorrect.

What I might suggest for clarity is to say 'Any HF 3-30 Mhz' which is somewhat better.

For those modes that aren't ham-related nor broadcast-related, (or higher than 30 Mhz), the Utility DXers Forum Yahoo group is really the place to check for things like this. It's a very active group and has LOTS of digital stuff reported very frequently

OK this a bit more of a thorny problem. There are 2 articles - 'Cuban Numbers Station HM01' and 'DIGTRX' which basically describe the same thing. I can convert one article, but the other is unnecessarily redundant and not needed.

The first question is the reference that should be used- since many of the HF data listed on this page are named by their mode, I would suggest which ever page is to be created would be called RDFT

The next question is which article should be converted? Which ever one I convert, there will still be the other which is unneeded. Mike

Pick whichever one you feel would be the least work in redoing. I'll handling the article merging for the other article.

Do try to keep as much content that's relevant as possible in the article, (like, for example, leave the DIGITRX waterfall and sound sample and list it as one example of RDFT in a section). Discarding precious information means more time putting it back in later :p. And details are always a plus.

All the signals described here seem to center on one frequency, or on a small set of frequencies. I frequently hear an HF signal, usually on 40m, that consists of digital "noise", rather loud, that either increases or decreases frequency very slowly (maybe by one to ten Hz per second). It never seems to interfere with amateur QSOs, maybe because it doesn't stay on one frequency for long. I can't determine the modulation mode just by listening to the audio. -- David Spector, Southern Maine, USA.

There are also, and I've seen these on the websdr at Univ. of Twente, lots of freq hopping blips, that im sure are coming from radars or research transmitters. Those are a bit harder to categorize, since documentation on them may be sparse to non-existant, and tracking them may even be harder

All right, I did the move of the Cuban article, rewrote it, combining the DIGTRX article and the data I had - the move didn't take. No new entry was posted on the main page; however there is a redirect from the Cuban link to the RDFT article.

The move did take. The homepage, as stated before, does not update in real time. It takes a day (about 3-6am EST is when the sync happens from my estimates) for the homepage to update. I checked the logs and you moved the Cuban page to RDFT, as stated.

In about a day, the old Cuban link will be removed, and RDFT will be added to the home page in it's place, assuming you kept the "Category:Signal" tag in the article.

Notice that an article I'm currently working on, SSTV (Slow-Scan Television) is not on the home page, despite being made. Without the Signal tag, it will not be read by the server to be added to the main page.

Haha, thanks! I actually saw the second one. I plan on spending a lot of time with fldigi to make waterfalls for these modes. Its what i've been looking for to use for MFSK. I'm still debating how I will organize this large collection of signal modes, since in reality, only a handful are used with any frequency (PSK31, MFSK16, etc)

Just letting you know that we'll be making changes to the wiki over the next few days to add some features like forms (so users who don't know wiki syntax can add a signal easily), and to implement things like frequency ranges on the main page for Artemis etc. So during this time the wiki might look a little broken. You can still add information to the wiki, but just be aware that the main template will be changing soon. When its done i'll make sure all the pages are updated and cleaned up.

Cartoonman - there are a lot of screenshots and audio samples of MFSK stuff on the fldigi site as well - just pick that from the left panel.

If you're up for fixing the main page along with the upgrades, I'd like to send you a list - there's a fair amount of misunderstandings and stuff that's just wrong - but it's way too much to put on a simple text messenger like this. To where should I send it?

And thanks for that link! I haven't seen this before but I have taken a look at some of the links they have.

When I wrote these articles, the main goal was primarily to get the signal up on the site (properly ID'd as much as I could verify), and put some information I found with it. Fact checking would simply take too much time and would end up with even slower submissions of signals than I am currently doing now. I would love to have other users write up factually correct and accurate descriptions for these signals, as it frees up my time to focus on IDing and adding signals, including getting good audio samples and waterfall images. A lot of my time is spent just trying to verify if the signal I have is what I think it is.

Btw, this isn't to say I don't fact check at all, I do fact check, but understand that I commonly find conflicting sources on information for these signals so it becomes a rather involved task sifting through misinformation; its inevitable that some will get through.

The last signal "weird moving signal" I know EXACTLY what that is, it is an OLD type of telemetry signal used to remotly send the value displayed on a gauge or dial, It works by taking the circular movement of a needle on a dial (like a thermometer or pressure gauge) and connecting the shaft to a potentiometer and using the pot to control a VCO, you get the data by knowing the "center" frequency and calculating the offset value of the Continuous signal as it moves up and down, the ammount it moves is displayed at the RX end by taking the difference in frequency and using that value to move a dial on a gauge.

1 fucking dollar to upload a god damn file to your shit site. Everyone is just trying to help everyone out and you have to pull this greedy eurotrash bullshit. don't even try to pull the web hosting cost bullshit because we all know its crap. if you really cant afford it take the fucking site down.

Apparently, if you aren't signed in, and you try to upload a file into the form, it says "You must $1 to upload". Must be because non-registered users cannot upload, so there's some bug when they're given an upload screen.

obviously like your website however you need to check the spelling on several of your posts. Several of them are rife with spelling issues and I to find it very bothersome to tell the truth on the other hand I will definitely come again again.

This site is fantastic but could really be developed - there are so many different types of signal - if I catch something that I can tell is a certain type of stanag for example, or some particular type of modem, better to help newbies and radio pros navigate quickly to the signal they're looking for rather than have to scroll through all the stuff above..

I've had plans to figure out a way to rework the Category system so that we can begin to group signals up based on key features so that it is easier to navigate and find signals of interest. In the past the biggest obstacle was not having enough variety of signals for this to really be useful, but now with over 150 signals, we have enough sample size to make some useful categories.

Currently the category system is a bit problematic as it shares labels with server-based signal and unid signal tags, so it will be messy to create one based on the current system. Descriptive tags will have to be placed in a different category type of sorts.